Brake drums are cast gray iron drums attached to a wheel or a shaft so that its motion may be retarded by the application of an external band or internal brake shoes. Brake drums, especially those made for the trucking industry, must be durable and capable of rapidly and effectively dissipating the heat that builds up when the external band or shoe is applied during braking operations.
Cast gray iron has been the material of choice for producing brake drums. This material exhibits high strength and is resistant to wear under high stress conditions. In addition, cast gray iron readily dissipates heat and is ideally suited for the production of brake drums.
In recent years there has been a concerted effort to increase the efficiency of automotive vehicles, including but not limited to, the reduction of weight without loss of performance. Efforts have been made to employ lightweight materials for the body of automotive vehicles as well as for functioning parts of the vehicle. For example, fiberglass has been used to replace heavier steel and cast gray iron in portions of the body of the vehicles. In addition, aluminum has been used to fabricate engines to replace engines made of cast gray iron.
As previously indicated, cast gray iron has been used to produce brake drums. This material, however, is heavy and makes brake drums a significant contributor to the weight of an automotive vehicle. It would therefore be a significant advance in the art of producing automotive vehicles and particularly for the production of brake drums if a material could be developed which performed at least as well as cast gray iron but was significantly lighter than this material in the production of brake drums.